Bump superagent from 2.3.0 to 6.1.0
Bump superagent from 2.3.0 to 6.1.0

Bumps [superagent](https://github.com/visionmedia/superagent) from 2.3.0 to 6.1.0.
- [Release notes](https://github.com/visionmedia/superagent/releases)
- [Changelog](https://github.com/visionmedia/superagent/blob/master/HISTORY.md)
- [Commits](https://github.com/visionmedia/superagent/compare/v2.3.0...v6.1.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
janusvr/janus-server,timschwartz/janus-server,timschwartz/janus-server,janusvr/janus-server